The arm is divided by a fascial layer (known as lateral and medial intermuscular septa) separating the muscles into two osteofascial compartments: the anterior and the posterior compartments of the arm.

The fascia merges with the periosteum (outer bone layer) of the humerus. The compartments contain muscles which are innervated by the same nerve and perform the same action.

Being a key element to support the spine and contribute to a good posture, it is important to properly exercise the abdominal muscles together with the back muscles as when weak or overly tight they can suffer painful spasms as well as injuries.

When properly exercised, these muscles contribute to improve posture and balance, reduce the likelihood of back pain episodes, reduce the severity of back pain, protect against injury by responding efficiently to stresses, help avoid some back surgeries, and help healing from a back problem or after spine surgery. Also, when strengthened, the abdominal muscles provide flexibility as well.

A variety of resistance exercises can be used to train the pectoralis major, including bench pressing (using dumbbells, barbells or machines at various angles such as decline, incline and flat where the hips are above, below and level with the head respectively), push ups, flyes (using dumbbells or machines at either flat or inclined angles), cable crossovers or dips.

Multi-joint press exercises are better for building muscle mass, while fly and crossovers are more suited for shaping and increasing striations. This muscle is often said to consist of four portions (upper, lower, inner and outer) but the pectoralis actually contracts evenly across all heads during most exercises and as such no portion can be 'targeted'.

There are several muscles in which to target during back exercises including the latissimus dorsi (the large muscles on either side of the back), rhomboids and trapezius muscles (upper back muscles) and erector spinae (lower back).

It's important to work all areas of the back when strength training, so try choosing a variety of exercises to target the upper, mid and lower back areas.